Hi everyone,
I posted the below at the rx8forum (http://www.rx8forum.com/showthread.p...3269#post13269)
The renesis works much like other internal combustion engines by igniting an air-fuel mixture and using the expansion to do mechanical work. How can engines make more power?
1. More displacement - Is there no replacement?
2. Better volumetric efficiency - How much air can we get in the engine?
a. Stuff more air into the engine (ie. turbocharging, supercharging, Nitrous, Miller cycle?) More air is good. Compressing air also heats it though.
b. Cool the incoming air (ie. intercoolers, nitrous) Cool air is good because it is more dense.
c. Let more air into the engine. (ie. dual intake valves, tuned intake manifolds) More air is good.
d. Let exhaust leave the engine easier - (ie. dual exhaust valves, headers, high flow exhaust) More bad air going out means more good air can come in. More air is good.
3. Better use of the air/fuel mixture for power (Thermal efficiency)
a. Higher compression ratios. The air-fuel mix will be more prone to detonation & will need higher octane gas though.
b. Better thermal efficiency
c. Improved fuel atomization
d. More powerful spark
e. Better combustion stability
4. Less friction / resistance to movement (Mechanical efficiency)
a. Use lighter weight moving parts - waste less energy
b. Improve pumping losses (ie. Miller cycle with shorter compression stroke than expansion *huh?*)
How and why does a renesis make more power than previous rotaries?
1. Larger displacement - No.
2. Better volumetric efficiency
a. The side exhaust allows an intake port approx 100% bigger than previous production rotaries.
b. The side exhaust allows an exhaust port approx 30% bigger than previous production rotaries. Unfortuately, the port is not open as long as previous production rotaries and the exit path for exhaust is not as straight.
c. The intake manifold has been greatly improved to provide laminar airflow and uses 3 different length paths to tune the dynamic effect of the intake air pulses. This improves the supply of air to the engine for the entire powerband.
3. Better thermal efficiency
a. Better atomization of fuel due to ultra fine fuel injectors
b. More powerful spark due to higher power coils
c. Higher compression (unknown how high?) - [limited by sealing improvements and reliability]
d. Improved combustion stability/efficiency at low speed & light load due to no overlap.
e. Better thermal efficiency due to longer power stroke (exhaust port opens later)
f. Better thermal efficiency due to possible use of cermet (ceramic/metal hybrid alloy)?
4. Better mechanical efficiency
a. 14% Lighter rotors. Rotors will be approx 8.2 lb (9.54 * .86) leading safely to higher revs.
b. Shorter and lighter driveshaft. Carbon-fiber driveshafts are cool.
What else am I missing? I believe the side exhaust design was never used in the past because the peripheral exhaust offered a straighter path and led to greater power. While I'm sure that peripheral port rotaries with port jobs are capable of at least as much power as the renesis, we should congratulate Mazda on their R&D of the side exhaust port renesis since we can now have a rotary with larger ports AND greater fuel economy and emissions.
Brian